It is "The Eight Tribes of the Dragon: Wu Dalang Liangshan Conquers the Song Dynasty", author: Lou Wan

Chapter 38: Cave Heaven and Paradise! The countless caves lead to tranquility, and fish swim in the Crystal Palace!

He was reincarnated into the late Northern Song Dynasty and became Wu Dalang. He was proud of the Eight Tribes of the Dragon and led the Lingjiu Palace masters and Liangshan generals to overthrow the Northern Song Dynasty and set sail on expeditions.